Warning to users of pre-release versions of Windows Vista: In two days, your operating system will self-destruct, like the cassette tape at the beginning of Mission: Impossible.

As reported earlier, tomorrow, May 31, is the last day of full functionality for Customer Preview Program versions of Vista. That includes Vista beta 2, and both release candidates.

The OS will gradually shut itself down in stages, and do it in an unusual way: Starting Friday, a user can log on to the OS for two-hour sessions only. After two hours, the OS will automatically reboot, without offering a chance to save. That leaves a two-hour window to save work, transfer settings and so on to another OS. Any work not finished within that span will be lost when the machine reboots.

That cycle will last until Aug. 28, after which time the OS will shut down for good.
Users of pre-release versions can upgrade to RTM versions of Vista, or do a clean install of earlier Windows versions, like XP. Vista pre-release does not offer a "roll-back" ability to return to an earlier OS.

Notices started popping up in the Vista interface, warning about the impending reboots, on May 18. Vista Product Manager Nick White, on a Vista blog, put it succinctly for those still running a pre-release version: "Please, do yourself a favor and upgrade to any edition of the RTM version of Windows Vista before 31 May."

Microsoft updated an August security advisory this week to urge organizations using the Lightweight Directory Access Protocol in supported Windows systems to implement some configuration changes manually.